The initial pathophysiologic response to major burn injury is being studied in experimental burns and man. Fluid resuscitation regimens developed from measurements of extracellular fluid volume, blood volumes, and cardiac outputs are used as a baseline for study of the internal distribution of fluid and electrolytes between the intracellular and extracellular fluid (transmembrane potential measurements plus tissue volume - electrolyte composition). Integrated studies of the circulatory response and hematologic response (both formed elements and clotting studies) and their role in modifying fluid and electrolyte responses are designed to identify the circulating myocardial depressant of burn shock and to define and identify the role of various fibrinogen degradation products in the systemic response and in burn wound edema formation.